Laminated visco-elastic support

ABSTRACT

A laminated support for pressure-relief comprising an upper layer of visco-elastic foam, a middle layer of visco-elastic foam having a greater hardness, and a bottom layer of highly resilient polyurethane foam. These layers are sandwiched between two layers of reticulated filter polyurethane foam.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This is a continuation of co-pending U.S. patent application Ser.No. 09/703,893, which was filed on Nov. 1, 2000, now U.S. Pat. No.6,541,094, which issued on Apr. 1, 2003, and is a continuation of U.S.Pat. No. 6,159,574, which issued Dec. 12, 2000, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The invention relates to mattresses and cushions, and moreparticularly to supports made of visco-elastic material.

[0004] 2. Related Prior Art

[0005] Mattresses and cushions used every day in homes and hospitals arenot well-suited for people requiring pressure-relief. In hospitals, forexample, long-term patients often suffer from pressure sores.

SUMMARY OF THE INVENTION

[0006] Known supports made of standard polyurethane foam do not provideeven or well-distributed support of a body reclining thereon because ofthe polyurethane material. Such known standard supports have aspring-like characteristic that tends to return an increased reactiveforce in response to increasingly large forces on the support. Moreover,the greater the deflection of the polyurethane support, the greater thereactive force provided by the standard support. This spring-likecharacteristic is undesirable in the case of long-term patient carebecause the points at which the greatest pressure occurs are the pointsat which pressure sores can be formed.

[0007] Changing the density of the standard polyurethane foam used insuch known supports does not improve the performance of such knownsupports. For example, use of a lower density foam requires a thicker,bulkier cushion or mattress, which can easily become unwieldy orunstable, and can still result in pressure points because of theinherent spring-like nature of the polyurethane foams. Also, if asufficiently large force is applied to a support made of low densitypolyurethane foam, it is possible that the force will “bottom out” oract through the support and onto whatever structure lies below or behindthe support.

[0008] The present invention therefore seeks to provide improvedsupports, such as mattresses and cushions, for pressure-relief.

[0009] According to the present invention there is provided a laminatedsupport for pressure-relief comprising at least two layers of foamadhered together, wherein at least one layer is a visco-elastic foam.

[0010] In one embodiment, the laminated support comprises two layers ofvisco-elastic foam adhered together, wherein one layer of visco-elasticfoam has a greater hardness than the other layer. The laminated supportmay further comprise a layer of polyurethane foam adhered to the layersof visco-elastic foam.

[0011] In another embodiment, the laminated support comprises a singlelayer of visco-elastic foam and a single layer of polyurethane foamadhered together.

[0012] The visco-elastic properties of the laminated support respond toa combination of body weight and body temperature. In particular,visco-elastic foam supports tend to soften when heated, and thereforetend to soften in response to body heat. As a result, relatively hardvisco-elastic material will initially firmly support a body lyingthereon and will soften at the pressure points. Thus, the supportsubsequently gently molds to the form of the body, allowing pressure tobe absorbed uniformly and distributed evenly across the support. Thisproperty is of particular benefit in the prevention and healing ofpressure sores.

[0013] Other features and advantages of the invention will becomeapparent to those skilled in the art upon review of the followingdetailed description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 shows a side view of a support embodying the presentinvention.

[0015]FIG. 2 shows a side view of a support that is an alternativeembodiment of the present invention.

[0016]FIG. 3 shows a side view of a support that is a second alternativeembodiment of the present invention.

[0017]FIG. 4 shows a side view of a support that is a third alternativeembodiment of the invention.

[0018]FIG. 5 is a perspective view in partial cross section of thesupport shown in FIG. 1.

[0019]FIG. 6 is a perspective view in partial cross section of thesupport shown in FIG. 2.

[0020]FIG. 7 is a perspective view in partial cross section of thesupport shown in FIG. 3.

[0021] Before one embodiment of the invention is explained in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangements of the componentsset forth in the following description or illustrated in the drawings.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is understood that thephraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The support or cushion A shown in FIGS. 1 and 5 includes a bottomlayer 1 of 40 mm thick visco-elastic foam having a density of 110 kg/m³and a hardness of 30N, and a top layer 2 of 10 mm thick visco-elasticfoam having a density of 85 kg/m3 and a hardness of 10N.

[0023] The support B shown in FIGS. 2 and 6 is well-suited for use as anoverlay which can be placed on top of an existing mattress to provideextra comfort and pressure-relief. The overlay B includes a bottom layer3 of 60 mm thick visco-elastic foam having a density of 83 kg/m³ and ahardness of 13N, and a top layer 4 of 10 mm thick visco-elastic foamhaving a density of 83 kg/m³ and a hardness of 10N. A support similar tothe construction of support B could also be manufactured to include abottom layer of 80 mm thick highly resilient polyurethane foam having adensity of 35 kg/m³ and a hardness of 12N, and a top layer of 70 mmthick visco-elastic foam having a density of 82 kg/m³ and a hardness of13N.

[0024] The support C shown in FIGS. 3 and 7 is well-suited for use as amattress and includes a bottom layer 5 of 75 mm thick polyurethane foamhaving a density of 35 kg/m³, a middle layer 6 of 60 mm thickvisco-elastic foam having a density of 83 kg/m³ and a hardness of 13N,and a top layer 7 of 10 mm deep visco-elastic foam having a density of83 kg/m³ and a hardness of 10N.

[0025] Suitable polyurethane foams are manufactured by A/S Dan-Foam,5560 Arup, Denmark. One example of a polyurethane foam has themanufacturer's code HE35S.

[0026] Similarly, suitable visco-elastic foams are made by A/S Dan-Foam,5560 Arup, Denmark and sold under the trade mark TEMPUR. One suchvisco-elastic foam has the manufacturer's code T-85. A preferred rangeof density of the visco-elastic foam is 50 to 120 kg/m³.

[0027] For each of the above embodiments A, B, and C, the layerscomprising the cushion, overlay or mattress, are adhered together usingan environmentally-friendly water-based adhesive such as SABA AQUABONDRSD (trade mark), a two-component water-based adhesive produced by SABADINXPERLO BV, B-7090 AA DINXPERLO, Belgium. Hardness is to be measured65% compression at 20° C.

[0028] For each of the above embodiments A, B, and C, the layerscomprising the cushion, overlay or mattress, once the appropriate layersof foam have been adhered together, a 2 mm thick sheet 8 of areticulated filter polyurethane foam is adhered to each outer face ofthe laminated support. This layer 8 is air permeable.

[0029] The support D illustrated by FIG. 4 includes a single layer ofvisco-elastic foam sandwiched between two layers of reticulated filterpolyurethane foam. In particular, the support D includes a sheet ofvisco-elastic foam 9, which is sandwiched between two sheets ofreticulated polyurethane foam 8. The sheet of visco-elastic foam 9preferably has a thickness ranging from 50 mm to 150 mm, a densityranging from 50 kg/m³ to 120 kg/m³, and a hardness ranging from 10N to30N measured at 65% compression at 20° C.

[0030] Any of the supports A, B, C, and D may be provided with an outercovering (not shown). Two examples of outer coverings are describedbelow.

[0031] One example is a textile net cover followed by a removable outerfabric cover. The textile net cover eases the taking on and off of thefabric cover and is made from a specially treated textile which allowsthe foam layers to ‘breathe’ whilst preventing contamination of the foamlayers by fluids. An example of such netting is the 100% cotton nettingmanufactured by BIDET & HORST GmbH & Co KG, D-4460 Hörstel, Germany.

[0032] A second example of an outer covering is a waterproof,vapor-permeable cover made of base nylon fabric coated with polyurethanefilm. Preferably, this cover material is 0.25 mm thick, weighs 245 g/m²,and is constructed having a single sheet top surface, no joins, weldedseams and a sealed zip flap. In addition, this cover may be pretreatedwith an anti-bacterial agent.

[0033] The laminated support of the present invention, when covered withthe polyurethane coat nylon material ensures good hygiene for patientswith incontinence. The elasticity of the cover allows thepressure-relieving properties of the visco-elastic foam to beunimpaired.

[0034] Laminated supports manufactured in accordance with the presentinvention allow air to circulate around a patient's skin and thus avoidthe discomfort of perspiration and skin irritation.

[0035] The visco-elastic foam layers provide the laminated support withits special pressure-relieving properties. The support is thus able tomould according to the weight and temperature of a body in contacttherewith. When the body is moved from a particular point of contact,the support quickly regains its initial shape, ready to be re-molded.

[0036] This property of the support is different from normallypolyurethane foams which bulk up when compressed, thereby exertingpressure rather than relieving it. As a result, the quality of sleep ofa person reclining on a support constructed of layers of foam havingvisco-elastic properties is different from normal polyurethane foamswhich bulk up when compressed, thereby exerting pressure rather thanrelieving it.

[0037] In use, it is the side of the support which has the visco-elasticfoam layer, or the softest visco-elastic foam layer, foremost which isarranged for contact with a person's body. As a result, the support doesnot need to be turned, as is customary with hospital mattresses, forexample.

[0038] Various features of the invention are set forth in the followingclaims.

1. A laminated support for pressure-relief comprising at least twolayers of foam adhered together wherein at least one layer consists of avisco-elastic foam.
 2. A laminated support as claimed in claim 1comprising two layers of visco-elastic foam adhered together wherein onelayer of visco-elastic foam has a greater hardness than the other layer.3. A laminated support as claimed in claim 1 comprising a layer ofvisco-elastic foam and a layer of polyurethane foam adhered together. 4.A laminated support as claimed in claim 2 further comprising a layer ofpolyurethane foam adhered to the layer of visco-elastic foam having thegreater hardness.
 5. A laminated support as claimed in claim 4 wherein alayer of reticulated filter polyurethane foam is adhered to the freeface of each outer foam layer.
 6. A laminated support as claimed inclaim 5 which is provided with a waterproof vapor-permeable outer cover.